4
4 Tollens’ Test Tollens’ reagent, which contains Ag +, oxidizes aldehydes, but not ketones. Ag + is reduced to metallic Ag, which appears as a “mirror” in the test tube.

5
5 Tollens’ reagent detects an aldehyde Tollens’ reagent (a solution of Ag + in aqueous NH 3 ) can be used to detect the presence of the aldehyde group in the unknown sample. As the oxidation of the aldehyde proceeds, silver metal is deposited on the walls of the reaction flask as a shiny mirrow. If upon addition of the Tollens’ reagent to the unknown, the test tube becomes silvery, the unknown is an aldehyde. RCHO + 2Ag(NH 3 ) OH - → RCOO - + NH Ag + 3NH 3 + H 2 O anTollens’ salt of a silver aldehydereagentcarboxylic acid mirrow

6
6 Benedict’s Test Benedict’s reagent, which contains Cu 2+, reacts with aldehydes that have an adjacent OH group. When an aldehyde is oxidized to a carboxylic acid, Cu 2+ is reduced to give Cu 2 O(s).